Relays are part of a car’s electrical system. Without them, electrical components would not work.
Several electrical devices in a car run off relays.
WHAT IS A RELAY?
As its name suggests, it relays current from the battery to the device.
It may seem superfluous as any device would still function if wired directly from the battery. But there is a sound reason for using relays.
A relay is essentially a switch with an electromagnet inside. When energised, it triggers a lever to close the contacts of a circuit.
HOW DOES IT WORK?
Let’s use the car horn as an example.
When you press the steering-wheel boss to activate the horn, a small current – less than 0.5 amps – is sent from the horn switch to the relay.
The relay’s electromagnet then activates an internal switch, which bridges the main 12-volt supply to the horn’s terminal.
Most horns require at least 10 amps to work. If it is a twin-horn set-up, you are looking at 20 amps at least. A relay’s switch typically handles 30 to 40 amps.
WHAT’S THE ADVANTAGE OF A RELAY?
The horn button therefore does not need to be wired with high-current capacity wires. Nor does the horn switch need to endure the tens of amperes to power the horn.
This way, over time, wear and tear is confined largely to the relay instead of the wires.
Relays are workhorses that are usually installed close to the fuse box. They are easily removed. A horn relay typically costs about $5.
CHANGING RELAYS MAY SOLVE YOU CAR TROUBLE
As a car ages, certain devices may stop working or not work too well. The aforementioned car horn, for one, might suddenly not work.
But before you conclude that you need a new horn, get your car checked out by a mechanic. For all you know, a worn relay, which is easily replaced, could solve the problem.